Systems and methods related to switchable output stages in power amplifiers

ABSTRACT

Systems and method related to switchable output stages in power amplifiers. In some embodiments, a power amplifier (PA) circuit can include a driver stage configured to amplify a radio-frequency (RF) signal. The PA circuit can further include a plurality of output stages, with each output stage being configured to be capable of further amplification the RF signal. The PA circuit can further include a switch implemented to route the amplified RF signal from the driver stage to a selected one of the plurality of output stages, such that the selected output stage further amplifies the amplified RF signal.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application No.62/004,139 filed May 28, 2014, entitled SYSTEMS AND METHODS RELATED TOSWITCHABLE OUTPUT STAGES IN POWER AMPLIFIERS, the disclosure of which ishereby expressly incorporated by reference herein in its entirety.

BACKGROUND

Field

The present disclosure generally relates to switchable output stages inradio-frequency (RF) power amplifiers.

Description of the Related Art

In wireless communication applications, a radio-frequency (RF) signal tobe transmitted is typically generated by a transceiver. Such an RFsignal is typically amplified by a power amplifier (PA) before beingrouted to an antenna.

SUMMARY

According to some implementations, the present disclosure relates to apower amplifier (PA) circuit that includes a driver stage configured toamplify a radio-frequency (RF) signal, and a plurality of output stages,with each output stage being configured to be capable of furtheramplification the RF signal. The PA circuit further includes a switchimplemented to route the amplified RF signal from the driver stage to aselected one of the plurality of output stages, such that the selectedoutput stage further amplifies the amplified RF signal.

In some embodiments, the switch can include an input pole and aplurality of output throws corresponding to the plurality of outputstages. The plurality of output stages can include a first output stageand a second output stage. The switch can include a plurality ofswitching elements, with each switching element having one sideconnected to the input pole, and the other side connected to thecorresponding throw.

In some embodiments, each of the plurality of output stages can beconfigured to be capable of being connected to a corresponding antenna.The corresponding antenna can be unique to each output stage.

In a number of implementations, the present disclosure relates to afront-end architecture for a wireless device. The front-end architectureincludes a power amplifier (PA) configured to amplify a radio-frequency(RF) signal for transmission. The PA includes a driver stage and aplurality of output stages. The front-end architecture further includesan RF switch configured to route a partially amplified RF signal fromthe driver stage to a selected one of the plurality of output stages,such that the selected output stage further amplifies the partiallyamplified RF signal. The front-end architecture further includes aplurality of antennas including a selected antenna coupled to theselected output stage to facilitate transmission of the amplified RFsignal through the selected antenna.

In some embodiments, the front-end architecture can further include aswitching network configured to route the amplified RF signal from theselected output stage to the selected antenna. The front-endarchitecture can further include a low-noise antenna (LNA) configured toreceive and amplify a received RF signal from an antenna among theplurality of antennas. The switching network can be further configuredto route the received RF signal from the antenna to the LNA. Thefront-end architecture can be configured to operate in a time-divisionduplexing (TDD) mode.

In some embodiments, the PA can be part of a transmit (Tx) circuit. TheTx circuit can include a Tx switch implemented between an output of thecorresponding output stage and the corresponding antenna. In someembodiments, the PA may not be coupled to a receive (Rx) circuit so thata Tx switch is absent between an output of the corresponding outputstage and the corresponding antenna.

In some embodiments, the RF switch can include an input pole coupled tothe driver stage, a first throw coupled to a first output stage, and asecond throw coupled to a second output stage. The switching network caninclude a first Tx switch between the first output stage and a firstantenna, a second Tx switch between the second output stage and a secondantenna, a first Rx switch between the first antenna and the LNA, and asecond Rx switch between the second antenna and the LNA. Each of thefirst Rx switch and the second Rx switch can be in an OFF state during atransmit portion of the TDD operation. A selected one of the first Txswitch and the second Tx switch can be in an ON state and the other Txswitch can be in an OFF state during the transmit portion, with theselected Tx switch corresponding to the selected output stage.

In some embodiments, each of the first Tx switch and the second Txswitch can be in an OFF state during a receive portion of the TDDoperation. A selected one of the first Rx switch and the second Rxswitch can be in an ON state and the other Rx switch can be in an OFFstate during the receive portion, with the selected Rx switchcorresponding to the antenna providing the RF signal to the LNA.

In some embodiments, each of the first Tx switch, the second Tx switch,the first Rx switch, and the second Rx switch can include one or morefield-effect transistors (FETs) connected in series. The number of FETsin each of the first Rx switch and the second Rx switch can be greaterthan the number of FET(s) in each of the first Tx switch and the secondTx switch.

In some embodiments, the switching network can include a first Tx switchbetween the first output stage and a first antenna, a second Tx switchbetween the second output stage and a second antenna, a first switchableshunt path between the first antenna and a ground, and a secondswitchable shunt path between the second antenna and the ground. Each ofthe first switchable shunt path and the second switchable shunt path caninclude a quarter-wave transmission line. The front-end architecture canfurther include a shunt switch configured to switchably connect thefirst switchable shunt path and the second switchable shunt path to theground.

According to some teachings, the present disclosure relates to a methodfor operating a radio-frequency (RF) system. The method includesamplifying a radio-frequency (RF) signal in a driver stage of a poweramplifier. The method further includes routing the RF signal from thedriver stage to a selected one of a plurality of output stages, suchthat the selected output stage further amplifies the RF signal. Themethod further includes routing the RF signal for transmission from theselected output stage to a selected one of a plurality of antennas.

In some implementations, the present disclosure relates to aradio-frequency (RF) module that includes a packaging substrateconfigured to receive a plurality of components, and a power amplifier(PA) circuit implemented on the packaging substrate. The PA circuit isconfigured to amplify an RF signal for transmission, and includes adriver stage and a plurality of output stages. The RF module furtherincludes an RF switch implemented on the packaging substrate. The RFswitch is configured to route a partially amplified RF signal from thedriver stage to a selected one of the plurality of output stages, suchthat the selected output stage further amplifies the partially amplifiedRF signal. The RF module further includes a plurality of antenna portshaving a selected antenna port that is coupled to the selected outputstage to allow routing of the amplified RF signal to a selected antenna.

In some embodiments, the PA circuit can be implemented on a first dieand the RF switch can be implemented on a second die. In someembodiments, the PA circuit and the RF switch can be implemented on acommon die.

In accordance with some implementations, the present disclosure relatesto a wireless device that includes a transceiver configured to processradio-frequency (RF) signals, and a plurality of antennas configured tobe capable of being coupled to the transceiver. The wireless devicefurther includes a front-end module (FEM) in communication with thetransceiver and the plurality of antennas. The FEM includes a poweramplifier (PA) circuit configured to amplify an RF signal fortransmission. The PA circuit includes a driver stage and a plurality ofoutput stages. The FEM further includes an RF switch configured to routea partially amplified RF signal from the driver stage to a selected oneof the plurality of output stages such that the selected output stagefurther amplifies the partially amplified RF signal. The FEM furtherincludes a plurality of antenna ports corresponding to the plurality ofoutput stages such that the amplified RF signal from the selected outputstage is allowed to be routed to a selected one of the plurality ofantennas. In some embodiments, the transceiver can be configured tooperate in a time-division duplexing (TDD) mode.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show an example radio-frequency (RF) system where aswitching network can route an amplified RF signal to one of twoantennas, as well as route a received signal from one of the twoantennas for processing.

FIG. 2A shows an example power amplifier (PA) circuit having an outputstage for each of a plurality of transmission paths, with the outputstages switchably coupled to a common driver stage.

FIG. 2B shows an example of how the switchable coupling of FIG. 2A canbe implemented.

FIG. 3A shows a PA circuit having one or more features as describedherein can include more than two output stages that are switchablycoupled to a common driver stage.

FIG. 3B shows an example of how the switchable coupling of FIG. 3A canbe implemented.

FIGS. 4A-4C show various operating modes of an example RF system thatcan include the PA circuit of FIG. 2A.

FIGS. 5A and 5B show that an example RF system that can be similar tothe example of FIGS. 4A and 4B, but without a receive path.

FIG. 6 shows an RF system that can be implemented as a more specificexample of the RF system of FIGS. 4A-4C.

FIG. 7 shows that in some embodiments, at least some routingfunctionality can be provided without switches utilizing, for example, aquarter-wave line for each of a plurality of receive paths.

FIG. 8 shows an RF system that can be implemented as another morespecific example of the RF system of FIG. 7.

FIG. 9 shows a process that can be implemented to operate an RF systemhaving one or more features as described herein.

FIG. 10 shows a process that can be implemented to fabricate a devicehaving one or more features as described herein.

FIG. 11 shows that in some embodiments, one or more features of thepresent disclosure can be implemented in a product such as a module.

FIG. 12 depicts an example wireless device having one or moreadvantageous features described herein.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Described herein are various examples of how power amplifier systems canbe configured to provide advantageous features such as reduced loss.

In antenna diversity applications involving a plurality of antennas, anoutput of a power amplifier (PA) is typically routed to a selectedantenna. For example, such a PA output can be routed to one of twoantennas. In some applications, such routing of an amplifiedradio-frequency (RF) signal is performed by an RF switch. FIGS. 1A-1Cshow an RF system 10 where an RF switch 18 performs routing of anamplified RF signal to one of two antennas 20, 22. The RF switch 18 canbe implemented as two separate switch elements 18 a, 18 b as shown, andsuch switch elements can be operated to provide desired routing ofsignals in the RF system 10. The amplified RF signal is shown to beprovided by a PA that can include a driver stage 12 and an output stage14. The PA can receive an RF signal to be amplified from a transceiver30.

In some embodiments, the transceiver 30 can be configured to operate ina time-division duplexing (TDD) mode, where transmission and receptionoperations are performed in an alternating manner typically throughalternating switching operation. Examples of such TDD operations aredescribed herein in greater detail. Although described in the context ofTDD examples, it will be understood that one or more features of thepresent disclosure can also be implemented in other types of RF systems,including those utilizing frequency-division duplexing (FDD) modes.

In FIGS. 1A-1C, the transceiver 30 is shown to receive a received signalthat has been amplified by a low-noise amplifier (LNA) 28. The LNA 28can be coupled to either of the antennas 20, 22 through a correspondingreceive (Rx) switch (24 or 26).

In FIG. 1A, the RF system 10 is shown to be in a transmit mode where anamplified RF signal from the output stage 14 is routed to the firstantenna 20. To facilitate such a transmission operation, both of the Rxswitches 24, 26 are opened. The RF switch 18 is shown to be in a statewhere the input pole is connected to the output stage 14, and a firstoutput throw is in communication with the first antenna 20. Such aswitching configuration can be achieved by closing the switch element 18a and opening the switch element 18 b. Accordingly, the amplified RFsignal follows a transmission path depicted as 40.

In FIG. 1B, the RF system 10 is shown to be in another transmit modewhere an amplified RF signal from the output stage 14 is routed to thesecond antenna 22. To facilitate such a transmission operation, both ofthe Rx switches 24, 26 are opened, similar to the example of FIG. 1A.The RF switch 18, however, is shown to be in a state where the inputpole is connected to the output stage 14, and a second output throw isin communication with the second antenna 22. Such a switchingconfiguration can be achieved by opening the switch element 18 a andclosing the switch element 18 b. Accordingly, the amplified RF signalfollows a transmission path depicted as 42.

In FIG. 1C, the RF system 10 is shown to be in a receive mode where areceived RF signal from the first antenna 20 is routed to the LNA 28. Tofacilitate such a receive operation, each of the RF switch 18, and thesecond Rx switch 26 is opened, and the first Rx switch 24 is closed. Forthe RF switch 18, each of the two switch elements 18 a, 18 b can beopened. Accordingly, the received RF signal follows a reception pathdepicted as 44. It will be understood that reception through the secondantenna 22 can be achieved in a similar manner.

In RF systems such as the example shown in FIGS. 1A-1C, a lossassociated with the RF switch (18) can be significant. For example, aswitch loss in a range of about 0.7 dB to 1 dB can be expected. When itis desired or required to deliver a given power at a selected antenna,such a switch loss typically makes it necessary for the PA to outputmore power. For example, an increase in output power of a PA to overcomea switch loss of 1 dB can translate to an increase in the PA's supplycurrent by about 25%. Such an increase in the supply current can haveundesirable effects, including, for example, reduced battery life inportable wireless devices.

In some embodiments, switching functionality for routing transmission RFsignals to different antennas can be implemented prior to an outputstage of a PA. FIG. 2A shows an example PA circuit 100 having an outputstage for each of a plurality of transmission paths. Such output stagescan be switchably coupled to an output of a common driver stage. Forexample, a driver stage 104 is shown to receive an RF signal through aninput path 102. The output of the driver stage 104 is shown to beconnected to a pole (P) of an RF switch 108 through path 106. Such aswitch can be, for example, a single-pole-double-throw (SPDT) switch,with the first throw (T1) being connected to an input of a first outputstage 112 (through path 110), and the second throw (T2) being connectedto an input of a second output stage 122 (through path 120). The outputof the first output stage 112 can be routed (through path 114) to afirst antenna (not shown in FIG. 2A) as described herein. Similarly, theoutput of the second output stage 122 can be routed (through path 124)to a second antenna (not shown in FIG. 2A) as described herein. In FIG.2A, the switchable output stages are collectively indicated as 140.

FIG. 2B shows an example of how the RF switch 108 of FIG. 2A can beimplemented. Two separate switch elements 108 a, 108 b can be coupled toa common node (P) on one side, and the other side of each switch elementcan be coupled to its respective node (T1 or T2). In the exampleconfiguration shown in FIGS. 2A and 2B, the switch element 108 a can beclosed, and the switch element 108 b can be opened, so as to connect thepole P to the first throw T1 to thereby route an RF signal through thefirst output stage 112. Similarly, to route an RF signal through thesecond output stage 122, the switch element 108 b can be closed, and theswitch element 108 a can be opened, so as to connect the pole P to thesecond throw T2.

Although various examples are described herein in the context of twooutput stages and corresponding antennas, it will be understood that oneor more features of the present disclosure can also be implemented in PAcircuits having more than two output stages. For example, FIG. 3A showsa PA circuit 100 where a third output stage 132 is implemented, suchthat its input is connected to a third throw of an RF switch 108 (e.g.,a SP3T switch) through path 130, and its output is coupled to an antenna(not shown in FIG. 3A) through path 134. The first and second outputstages 112, 122 can be configured similar to the example of FIG. 2A. InFIG. 3A, the switchable output stages are collectively indicated as 140.

FIG. 3B shows an example of how the RF switch 108 of FIG. 3A can beimplemented. Three separate switch elements 108 a, 108 b, 108 c can becoupled to a common node (P) on one side, and the other side of eachswitch element can be coupled to its respective node (T1, T2 or T3). Inthe example configuration shown in FIGS. 3A and 3B, the switch element108 a can be opened, the switch element 108 b can be closed, and theswitch element 108 c can be opened, so as to connect the pole P to thesecond throw T2 to thereby route an RF signal through the second outputstage 122. Similarly, to route an RF signal through the first outputstage 112, the switch element 108 a can be closed, and the switchelements 108 b and 108 c can be opened, so as to connect the pole P tothe first throw T1. Similarly, to route an RF signal through the thirdoutput stage 132, the switch element 108 c can be closed, and the switchelements 108 a and 108 b can be opened, so as to connect the pole P tothe third throw T3.

In various examples, switches such as RF switches are depicted anddescribed as SPDT or SPMT (multiple-throw) switches. It will beunderstood that such switches can be implemented in manners similar tothe examples of FIGS. 2B and 3B.

It is noted that in the example of FIG. 1, the RF switch elements 18 a,18 b need to block much higher power RF signals associated with theoutput stage 14. In the example context of MOS switches, such switchesneed to be constructed with many series devices to block the high peakRF voltages. In various configurations that utilize the configurationsof FIGS. 2 and 3, the RF switch elements 108 a, 108 b, etc. only need toblock much lower power RF signals (e.g., those from the driver stage104). Such power blocking requirements can be determined by, forexample, the receive signal levels and the TX level from the otheractive antenna due to coupling between the antennas. Such aconfiguration results in, for example, the switch elements 108 a, 108 b,etc. being able to be constructed with fewer series MOS devices. Suchfewer series MOS devices in turn can result in a much lower loss for theswitch element. In a receive mode, the signal level is typically verylow; and accordingly, very few series devices are required in switches108 a, 108 b, etc. Based on the foregoing, one can see that the TXselection switch 108 no longer needs to block very high RF power (andresulting peak voltages) associated with the output stages.

In some embodiments, each of the two output stages 112, 122 in theexample of FIG. 2 can have its own output match network, therebyresulting in an additional output match network associated with thesecond output stage. However, such an additional output match networkcan be implemented with relatively low-cost passive devices.

In some embodiments, the additive cost of a second output stage (e.g.,122 in FIG. 2) can be much less than the cost associated with ahigh-power RF switch (e.g., 18 in FIG. 1) (e.g., a gallium arsenide(GaAs) switch) which is no longer needed. Even accounting for the RFswitch 108 before the output stages, the cost associated with the secondoutput stage is not necessarily higher than a counterpart example ofFIG. 1.

Further, because of the reduced loss in the example of FIG. 2, theoutput stages can output less power (and thus be smaller), and can beoperated at a lower gain. Accordingly, each output stage (112 or 122) inFIG. 2 can be implemented smaller than the output stage 14 in FIG. 1.Such reduced size in the output stages can offset at least some of theadditional space needed for the second output stage 122.

FIGS. 4A-4C show an example RF system 160 that includes the PA circuit100 and its switchable output stages 140 as described in reference toFIG. 2. In FIGS. 4A-4C, an RF signal from a transceiver 150 is shown tobe provided to a driver stage 104 of a PA circuit through path 102 to bepartially amplified. The partially-amplified RF signal is shown to beprovided to a pole of an RF switch 108 through path 106. The RF switch108 can include a plurality of throws. For example, asingle-pole-double-throw (SPDT) switch can be utilized. The first throwis shown to be connected to an input of a first output stage 112 throughpath 110 to fully amplify the partially-amplified signal, when the poleis connected to the first throw. Similarly, the second throw is shown tobe connected to an input of a second output stage 122 through path 120to fully amplify the partially-amplified signal, when the pole isconnected to the second throw. In FIGS. 4A-4C, such switchable outputstages are collectively indicated as 140.

The first output stage 112 is shown to be switchably coupled to a firstantenna ANT1. For example, the first output stage 112 is shown to beconnected to a first Tx switch S1 through path 114, and the first Txswitch S1 is shown to be connected to the first antenna ANT1 throughpath 162. Accordingly, the first output stage 112 can be connected to ordisconnected from the first antenna ANT1 by having the first Tx switchS1 closed or opened, respectively.

Similarly, the second output stage 122 is shown to be switchably coupledto a second antenna ANT2. For example, the second output stage 122 isshown to be connected to a second Tx switch S2 through path 124, and thesecond Tx switch S2 is shown to be connected to the second antenna ANT2through path 164. Accordingly, the second output stage 122 can beconnected to or disconnected from the second antenna ANT2 by having thesecond Tx switch S2 closed or opened, respectively.

The transceiver 150 is shown to receive an amplified signal from an LNA172 through path 174. The LNA 172 is shown to receive as input areceived signal through path 170 from either the first antenna ANT1 orthe second antenna ANT2. To receive a signal from the first antennaANT1, a first Rx switch S3 in path 166 can be closed so as to connectthe first antenna ANT1 to the input path 170. Similarly, to receive asignal from the second antenna ANT2, a second Rx switch S4 in path 168can be closed so as to connect the second antenna ANT2 to the input path170.

In FIG. 4A, the RF system 160 is shown to be in a transmit mode where anRF signal from the driver stage 104 is routed to the first antenna ANT1.To facilitate such a transmission operation, both of the Rx switches S3,S4 can be opened; the second Tx switch S2 can be opened; and the firstTx switch S1 can be closed. The RF switch 108 is shown to be in a statewhere the input pole is connected to the first throw and thereby to thefirst output stage 112. Accordingly, the partially-amplified RF signalfrom the driver stage 104 is shown to follow a transmission pathdepicted as 180, which includes the first output stage 112.

In FIG. 4B, the RF system 160 is shown to be in another transmit modewhere an RF signal from the driver stage 104 is routed to the secondantenna ANT2. To facilitate such a transmission operation, both of theRx switches S3, S4 can be opened; the first Tx switch S1 can be opened;and the second Tx switch S2 can be closed. The RF switch 108 is shown tobe in a state where the input pole is connected to the second throw andthereby to the second output stage 122. Accordingly, thepartially-amplified RF signal from the driver stage 104 is shown tofollow a transmission path depicted as 182, which includes the secondoutput stage 122.

In FIG. 4C, the RF system 160 is shown to be in a receive mode where areceived signal from the first antenna ANT1 is routed to the LNA 172. Tofacilitate such a receive operation, the first Rx switch S3 can beclosed; the second Rx switch S4 can be opened; and both of the Txswitches S1, S2 can be opened. Accordingly, the received signal from thefirst antenna ANT1 is shown to follow a reception path depicted as 184.It will be understood that reception through the second antenna ANT2 canbe achieved in a similar manner.

FIGS. 5A and 5B show an RF system 160 that can be similar to the exampleof FIGS. 4A and 4B, but without a receive path. More particularly, inthe example of FIGS. 5A and 5B, the Rx paths 166, 168 and relatedcomponents (e.g., S3, S4, LNA) of FIGS. 4A and 4B are absent. Such aconfiguration can be implemented in, for example, non-TDD applicationswhere a receive path is not needed or desired. Such a configuration canalso facilitate antenna diversity for Tx operations.

In FIG. 5A, the RF system 160 is shown to be in a transmit mode where anRF signal from the driver stage 104 is routed to the first antenna ANT1.To facilitate such a transmission operation, the second Tx switch S2 canbe opened; and the first Tx switch S1 can be closed. The RF switch 108is shown to be in a state where the input pole is connected to the firstthrow and thereby to the first output stage 112. Accordingly, thepartially-amplified RF signal from the driver stage 104 is shown tofollow a transmission path depicted as 180, which includes the firstoutput stage 112.

In FIG. 5B, the RF system 160 is shown to be in another transmit modewhere an RF signal from the driver stage 104 is routed to the secondantenna ANT2. To facilitate such a transmission operation, the first Txswitch S1 can be opened; and the second Tx switch S2 can be closed. TheRF switch 108 is shown to be in a state where the input pole isconnected to the second throw and thereby to the second output stage122. Accordingly, the partially-amplified RF signal from the driverstage 104 is shown to follow a transmission path depicted as 182, whichincludes the second output stage 122.

In the example of FIGS. 5A and 5B, it is noted that the TX selectionswitch 108 can be configured as described herein in reference to FIGS. 2and 3. It is further noted that the TX switches S1 and S2 can be omitteddue to the absence of Rx path(s). In such a configuration, efficiency ofthe transmitter can be higher due to removal of loss associated with S1and S2.

In the various examples described herein, it will be understood thatsome of all of the switches, including the switch 108 (e.g., FIGS. 2-5),can be implemented in, for example, MOS, GaAs or GaN processtechnologies. Other types of switches can also be utilized.

FIG. 6 shows an RF system 200 that can be implemented as a more specificexample of the RF system 160 described in reference to FIGS. 4A-4C. Forexample, each throw of the RF switch 108 can include one or more (e.g.,one or two) switching elements such as field-effect transistors (FETs)arranged in series as a stack (when more than one). Such low number ofswitching elements can be allowed due to, for example, the lower-poweredRF signals being switched.

In another example, the path 114 between the first output stage 112 andthe first Tx switch S1 can include a first output match network 202.Similarly, the path 124 between the second output stage 122 and thesecond Tx switch S2 can include a second output match network 212.

In yet another example, each of the first and second Tx switches S1, S2can include one or more (e.g., one or two) switching elements such asFETs 204, 214 arranged in series as a stack (when more than one). Asdescribed herein in reference to FIGS. 5A and 5B, such Tx switches mayor may not be present in configurations where Rx paths are not involved.

In yet another example, each of the first and second Rx switches S3, S4can include N switching elements such as FETs 220, 222 arranged inseries as a stack. The quantity N can be, for example 10. Such highernumber of FETs in a stack can provide isolation between the LNA and thehigh power RF signals being transmitted.

In the examples described in reference to FIGS. 4 and 6, the Rx switchesS3, S4 can allow routing of signals being transmitted and received. FIG.7 shows that in some embodiments, such routing functionality can beprovided without the Rx switches in an RF system 230. For example, aquarter-wave (λ/4) line can be provided for each of the receive pathsbetween their respective antennas and the input path to the LNA. In FIG.7, the first receive path 166 is shown to include a quarter-wave line232, and the second receive path 168 is shown to include a quarter-waveline 234. Such quarter-wave line can provide a shunt path 236 to groundwhen a shunt switch S5 is closed in a transmit state.

FIG. 8 shows an RF system 240 that can be implemented as a more specificexample of the RF system 230 described in reference to FIG. 7. Forexample, each throw of the RF switch 108 can include one or more (e.g.,one or two) switching elements such as field-effect transistors (FETs)arranged in series as a stack (when more than one). In yet anotherexample, each of the first and second Tx switches S1, S2 can include oneor more (e.g., one or two) switching elements such as FETs (204, 214)arranged in series as a stack (when more than one).

FIG. 9 shows a process 250 that can be implemented to operate an RFsystem having one or more features as described herein. In block 252, anRF signal can be partially amplified by, for example, a driver stage ofa PA circuit. In block 254, a switching operation can be performed toroute the partially amplified RF signal to a selected one of a pluralityof output stages of the PA circuit to generate an amplified RF signal.In block 256, a switching operation can be performed to route theamplified RF signal from the selected output stage to a correspondingantenna.

FIG. 10 shows a process 260 that can be implemented to fabricate adevice having one or more features as described herein. In block 262, apower amplifier (PA) circuit can be formed or provided, with the PAcircuit including a driver stage and a plurality of output stages. Inblock 264, a switching circuit can be formed or provided, with theswitching circuit including a pole and a plurality of throws. In block266, the pole of the switching circuit can be coupled to the driverstage, and the plurality of throws can be coupled to their respectiveinputs of the output stages. In block 268, a plurality of switches canbe formed or provided to allow connection of a selected output stage toa corresponding one of a plurality of antenna ports. Such antenna portscan be connected to their respective antennas.

FIG. 11 shows that in some embodiments, one or more features of thepresent disclosure can be implemented in a product such as a module 300.Such a module can be, for example, a PA module. The module 300 caninclude a packaging substrate 302 configured to receive a plurality ofcomponents. One of such components can be a PA circuit 100 having one ormore features as described herein. For example, the PA circuit 100 caninclude a driver stage and a plurality of output stages, and routing ofRF signals from the driver stage to the output stages can be facilitatedby an RF switch “S.”

In some embodiments, the PA circuit 100 can be implemented on a singlesemiconductor die. The RF switch S may or may not be included in such adie.

Another component implemented on the packaging substrate can be aswitching circuit 304. Such a switching circuit can include some or allof the various switches described herein. The switching circuit 304 mayor may not be included in the same die as the PA circuit 100.

The module 300 can further include one or more surface-mount devices(SMDs) 306. Such SMDs can include, for example, passive components tofacilitate various functionalities associated with the module 300.Although not shown in FIG. 11, the module 300 can further include, forexample, various conductor features, ground plane(s), contact pads, andconnection features (e.g., wirebonds or solder bumps) to facilitatevarious electrical connections, matching networks, etc.

In some implementations, device(s) and/or circuit(s) having one or morefeatures described herein can be included in an RF device such as awireless device. Such a device and/or a circuit can be implementeddirectly in the wireless device, in a modular form as described herein,or in some combination thereof. In some embodiments, such a wirelessdevice can include, for example, a base station configured to providewireless services, a cellular phone, a smart-phone, a hand-held wirelessdevice with or without phone functionality, a wireless tablet, etc.

FIG. 12 depicts an example wireless device 400 having one or moreadvantageous features described herein. In the context of various poweramplifier circuits and related switching functionalities as describedherein, a power amplifier (PA) circuit 100 is shown to include a driverstage and a plurality of output stages. Routing of RF signals from thedriver stage to the output stages can be achieved by an RF switch (S) asdescribed herein. Such a PA circuit can be part of a module 300 asdescribed herein. In some embodiments, the module 300 can be, forexample, a front-end module (FEM), and the FEM can include a switchingcircuit having one or more features as described herein. The FEM 300 canalso include an LNA 172. As described herein, duplexing of transmissionand reception can be achieved through the module 300 in a time-divisionduplexing (TDD) mode.

In the example wireless device 400, the PA circuit 100 can route RFsignals to a plurality of antennas (e.g., ANT1 and ANT2) through theplurality of output stages as described herein. Some or all of suchantennas can also be utilized for receiving of RF signals.

In the example wireless device 400, the PA circuit can receive an RFsignal to be amplified from a transceiver 414. The transceiver 414 canalso be configured to process received signals. Such received signalscan be amplified by the LNA 172.

The transceiver 414 is shown to interact with a baseband sub-system 410that is configured to provide conversion between data and/or voicesignals suitable for a user and RF signals suitable for the transceiver414. The transceiver 414 is also shown to be connected to a powermanagement component 406 that is configured to manage power for theoperation of the wireless device 400. Such a power management componentcan also control operations of the baseband sub-system 410.

The baseband sub-system 410 is shown to be connected to a user interface402 to facilitate various input and output of voice and/or data providedto and received from the user. The baseband sub-system 410 can also beconnected to a memory 404 that is configured to store data and/orinstructions to facilitate the operation of the wireless device, and/orto provide storage of information for the user.

A number of other wireless device configurations can utilize one or morefeatures described herein. For example, a wireless device does not needto be a multi-band device. In another example, a wireless device caninclude additional antennas such as diversity antenna, and additionalconnectivity features such as Wi-Fi, Bluetooth, and GPS.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A front-end architecture for a wireless device,comprising: a transmit circuit having a power amplifier configured toamplify a signal for transmission, the power amplifier including adriver stage and a plurality of output stages, the transmit circuitfurther including a switch configured to route a partially amplifiedsignal from the driver stage to a selected one of the plurality ofoutput stages, such that the selected output stage further amplifies thepartially amplified signal, the switch including an input pole coupledto the driver stage, a first throw coupled to a first output stage and asecond throw coupled to a second output stage; a plurality of antennasincluding a selected antenna coupled to the selected output stagethrough a switching network to facilitate transmission of the amplifiedsignal through the selected antenna, the switching network including afirst transmit switch between the first output stage and a firstantenna, a second transmit switch between the second output stage and asecond antenna; and a low-noise amplifier configured to amplify areceived signal from an antenna among the plurality of antennas, theswitching network further configured to route the received signal fromthe antenna to the low-noise amplifier, the switching network furtherincluding a first receive switch between the first antenna and thelow-noise amplifier, and a second receive switch between the secondantenna and the low-noise amplifier, the front-end architectureconfigured to operate in a time-division duplexing mode such that eachof the first receive switch and the second receive switch is in an OFFstate during a transmit portion of the time-division duplexingoperation, and a selected one of the first transmit switch and thesecond transmit switch is in an ON state and the other transmit switchis in an OFF state during the transmit portion, the selected transmitswitch corresponding to the selected output stage.
 2. The front-endarchitecture of claim 1 wherein each of the first transmit switch andthe second transmit switch is in an OFF state during a receive portionof the time-division duplexing operation.
 3. The front-end architectureof claim 2 wherein a selected one of the first receive switch and thesecond receive switch is in an ON state and the other receive switch isin an OFF state during the receive portion, the selected receive switchcorresponding to the antenna providing the received signal to thelow-noise amplifier.
 4. The front-end architecture of claim 1 whereineach of the first transmit switch, the second transmit switch, the firstreceive switch, and the second receive switch includes one or morefield-effect transistors connected in series.
 5. The front-endarchitecture of claim 4 wherein the number of field-effect transistorsin each of the first receive switch and the second receive switch isgreater than the number of field-effect transistor(s) in each of thefirst transmit switch and the second transmit switch.
 6. The front-endarchitecture of claim 1 wherein the switching network further includes afirst switchable shunt path between the first antenna and a ground, anda second switchable shunt path between the second antenna and theground.
 7. The front-end architecture of claim 6 wherein each of thefirst switchable shunt path and the second switchable shunt pathincludes a quarter-wave transmission line.